Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G4/00—Condensation polymers of aldehydes or ketones with polyalcohols; Addition polymers of heterocyclic oxygen compounds containing in the ring at least once the grouping —O—C—O—
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2/00—Addition polymers of aldehydes or cyclic oligomers thereof or of ketones; Addition copolymers thereof with less than 50 molar percent of other substances
  • C08G2/18—Copolymerisation of aldehydes or ketones
  • C08G2/22—Copolymerisation of aldehydes or ketones with epoxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2/00—Addition polymers of aldehydes or cyclic oligomers thereof or of ketones; Addition copolymers thereof with less than 50 molar percent of other substances
  • C08G2/18—Copolymerisation of aldehydes or ketones
  • C08G2/24—Copolymerisation of aldehydes or ketones with acetals

Definitions

• This invention relates to a process for the copolymerization of formaldehyde with cyclic ethers.
• the invention relates to a process for enhancement in the selectivity for the cyclic comonomer of the BF 3 -etherate- initiated reaction, in the presence of organic nitro compounds.
• BACKGROUND OF THE INVENTION It is known in the art that the copolymerization of cyclic ethers, notably dioxolane and ethylene oxide with formaldehyde, forms polyoxymethylene copolymers with improved thermal and base stability compared to those of polyoxymethylene homopolymer. For most applications, the desired composition range comprises ca.
• the cyclic ether concentration concentration in the hydrocarbon reaction medium had to be in the range of 0.5-1.0 M in order to achieve comonomer concentration in the copolymer of 0.5-2.5 mol-%.
• Dioxolane concentrations of that magnitude in the solvent represent a disposal or recycle problem.
• dioxolane there is formation of an unwanted side product - trioxepane to equilibrium levels of 0.3-2% by weight (0.02-0.15 M).
• the equilibrium concentration of the trioxepane is directly proportional to the dioxolane concentration in the solvent.
• the present invention avoids the recycle problem by improving the rate of cyclic ether, e.g., dioxolane, incorporation into the polymer by the addition of organic nitro compounds into the reaction. The process thus enhances the selectivity for the cyclic comonomer.
• polyoxymethylene copolymerizations use 1,3,5-trioxane and dioxolane as comonomers and Lewis acid initiators.
• Copolymerization of formaldehyde with cyclic ethers is less common.
• Polyoxymethylene can be produced from anhydrous formaldehyde anionically, via a reversible polymerization effected in a hydrocarbon slurry.
• the low solubility of formaldehyde in hydrocarbons and the formation of highly crystalline, insoluble polymer particles drive the equilibrium to both high conversion and high molecular weight.
• cyclic ether comonomers can copolymerize with formaldehyde in the hydrocarbon slurry process.
• Preferred initiators include triphenyl, and trimethoxyphenyl carbonium, and trialkyl oxonium salts of PFg and AsFg.
• This invention provides for a process for the copolymerization of anhydrous formaldehyde with cyclic ethers, the process comprising combining anhydrous formaldehyde with a slurry comprising particles of polyoxymethylene polymer or copolymer suspended in a hydrocarbon solvent having dissolved within it:
• Figure 1 shows a baffled 250 ml glass reactor immersed in a circulating water bath.
• Figure 2 shows a 800 ml jacketed baffled glass reactor through the jacket of which was passed water to control the temperature of the reactor.
• anhydrous formaldehyde having a maximum protonic impurity content of 600 ppm by volume, preferably 300 ppm by volume, is fed continuously from the gas phase into a hydrocarbon slurry at a temperature in the range of 30 to 80°C, preferably 50 to 70°C.
• the hydrocarbon slurry comprises a suspension of polyoxymethylene or copolymers thereof in a hydrocarbon solvent having dissolved therein dioxolane in the concentration range of 0.05 to 10% (0.05-1.0 M), preferably 1 to 5% by weight (0.1-0.5 M) and 0.5-10% (0.06-1.2 M), preferably 2-6% (0.2-0.7 M) by weight of nitromethane. Percentage by weight is stated as a percentage of the total weight of the hydrocarbon solution.
• BF ⁇ -diethyl or BF3-dibutyl etherate initiator is present in solution in the hydrocarbon at a concentration of 0.5 to 2 mM, preferably 0.8 to 1.2 mM.
• the polymer formed in the process of the present invention precipitates to increase the solids content of the slurry during semibatch copolymerizations.
• a portion of the solids formed is separated from the solvent by a filtration apparatus, with the solvent being recycled back to the polymerization unit.
• the hydrocarbon slurry comprises a suspension of the polyoxymethylene/dioxolane copolymer in a hydrocarbon liquid, preferably hexane, heptane, or cyclohexane. In the practice of this invention, it is found that a slurry comprising 5-40% by weight solids in n-heptane is found to be satisfactory.
• the dioxolane comonomer concentration in the hydrocarbon reaction medium had to be in the range of 3 to 10% by weight (0.5-1.0 M) in order to achieve comonomer concentration in the copolymer of 0.5-2.5 mol-%.
• Dioxolane residues and the formation of an unwanted side product - trioxepane to equilibrium levels of 0.3-2% by weight (0.02-0.15 M) results in a recycling problem.
• the equilibrium concentration of the trioxepane is directly proportional to the dioxolane concentration in the solvent.
• Organic nitro compounds suitable for the practice of the invention are nitroaliphatic species, including nitromethane, nitroethane, and nitrobutane, and nitrocyclohexane, as well as nitroaromatic species, including nitrobenzene and nitrotoluene. Nitromethane is preferred. Multi-nitro compounds are less preferred because their solubility is undesirably limited in the hydrocarbon solvents suitable for the practice of the present invention. Additionally, multi-nitro compounds may exhibit excessively acidic character leading to undesirable levels of chain transfer during polymerization, limiting polymer molecular weight.
• the polymer number average/weight average molecular weight is 20,000/95,000 as determined by gel permeation chromatography using hexafluoroisopropional solvent in the ASTM method D5296-92. This is significantly less than would be obtained in the presence of 3.5% by weight (0.38 M) of nitromethane in the solvent.
• Organic compounds of polarity similar to that of organic nitro compounds, for example, acetonitrile or dicyano butane, but not containing the nitro group, have not been observed to provide the benefits of the present invention. Some, e.g., dimethylsulfoxide or tetrahydrofuran, kill the reaction.
• Formaldehyde entered through port 3.
• Initial catalyst charge, thermocouple, slurry sample withdrawl, and liquid feeds during the run were done through septum 4.
• the reactor Prior to charging with the reactants, the reactor was dried under vacuum for 18 hours at 135°C in a model 1430 DuPont oven made by Sheldon Manufacturing, Inc. of Cornelius, OR.
• Formaldehyde was generated by thermolysis of 2-ethylhexylhemiformal and was determined by GC/MS (ASTM D4128-94 and D260) to contain less than 300 ppm by volume of water and methanol.
• the formaldehyde so generated was fed to the polymerizer by a peristaltic pump through large bore tubing.
• the oven- dried reactor was charged under nitrogen with the solvent and dioxolane as hereinbelow indicated. All liquid components, which includes solvent, dioxolane, and organic nitro compounds, were stored over size 4A activated molecular sieves from EM Science and determined by coulometric Karl-Fisher water analysis (ASTM El 064-92) to have the water content indicated hereinbelow.
• the solvent and dioxolane were heated to a temperature in the range of 40-50°C, the nitrogen purge removed, and formaldehyde introduced.
• Formaldehyde was flowed through the reactor for 0.5-1 min, with liquid agitation, followed by introduction of initiator via syringe through the septum port and commencement of dioxolane and organic nitro compound flows using syringe pumps to introduce them into the reactor via 1/16 inch stainless steel tubing through a septum port.
• initiator solution and additional solvent were also fed continuously.
• semibatch runs were also made, wherein the only continuous feed streams were the formaldehyde, organic nitro compound, if used, and dioxolane.
• the reaction temperature was observed to rapidly increase, at a rate proportional to the rate of reaction.
• the concentration of comonomer in the polymer was determined by dissolving the copolymer in acetic anhydride containing 2% by volume of sulfuric acid, followed by neutralization of the acid with calcium hydroxide, and then gas chromotographic analysis of the liquid layer to measure the relative amounts of diacetates present.
• the composition of the liquor collected with each slurry sample was detemined using an internal standard method and a centrifuge, when necessary, to give a separate liquid layer. Samples were injected into a gas chromatograph calibrated for the components present in the mixture.
• the polymer products including those from the small slurry samples collected for liquid and polymer analyses, were isolated by filtration, washed with methanol and acetone and dried under vacuum at room temperature.
• EXAMPLE 1 Into a rapidly stirred 1 liter reaction flask containing 102 g of heptane, 1.68 g (1.5 wt %) of dioxolane, 5.10 g (4.7 wt %) of nitromethane, the heptane being samrated with anhydrous formaldehyde at 40.2°C, was added 20 microliters of borontrifluoride diethyletherate. Dioxolane was then introduced continuously at a rate of 0.11 g/min, nitromethane at 0.62 g/min, and formaldehyde on demand.
• the reaction exotherm peaked at 57°C (the external bath was adjusted to maintain temperature near 56°C) and formaldehyde was consumed at an average rate of 1.32 g/min (8.5 g/min/1) over a 12 min. period.
• the final product was a copolymer containing 2.66 mole % of dioxolane derived units, a number average to weight average molecular weight ratio (Mn/Mw) of 45,900/133,000, a 83.6% base stability and a melting point of 161.6°C for the base stable fraction.
• the dioxolane concentration was 0.47 wt % and biproduct trioxane and trioxepane concentrations at the end of the reaction were 0.85 and 0.31 wt %.
• COMPARATIVE EXAMPLE 1 Into a rapidly stirred 1 liter reaction flask containing 250 g of heptane having a water content of 3.7 ppm, 12.91 g (4.9 wt %) of dioxolane with 10.0 ppm water, the heptane being saturated with anhydrous formaldehyde at 40°C was added 45 microliters of borontrifluoride etherate. Dioxolane was then introduced continuously at a rate of 0.17 g/min and formaldehyde was fed on demand. The reaction exotherm peaked at 46.5°C and formaldehyde was consumed at an average rate of 1.26 g/min (3.0 g/min/1) over a 30 min period.
• the final product was a copolymer containing 1.45 mole % of dioxolane derived units, an Mn/Mw ratio of 41,900/112,500, 88.0% base stability, and a melting point of 167.6°C for the base stable fraction.
• the average (equilibrium) dioxolane concentration was 5.5 wt % and biproduct trioxane and trioxepane at the end of the reaction were 0.76 and 0.46 wt %.
• the final copolymer contained 2.12 mole % of dioxolane derived units, an Mn/Mw ratio of 30,400/123,600, 87.1% base stability, and a melting point of 165.1 °C for the base stable fraction.
• Equilibrium dioxolane concentration was 1.0 wt % and biproduct trioxane and trioxepane at the end of the reaction were 0.73 and 1.0 wt %.
• COMPARATIVE EXAMPLE 2 The reaction was carried out, as in Example 2, except with 2.73 g (3.1 wt %) of acetontrile (in place of nitromethane) and 2.67 g (2.92 wt %) of initial dioxolane at 42.7°C. Formaldehyde was consumed at a rate of 0.88 g/min (6.32 g/min/1) and additional dioxolane was added at 0.24 g/min for 7.5 min (exotherm to 52.4°C).
• the final copolymer contained 0.539 mole % of dioxolane derived units, had an Mn/Mw ratio of 15.800/30,100, 51.7% base stability, and a melting point of 163.4°C for the base stable fraction.
• the equilibrium dioxolane concentration was 3.1 wt % and biproduct trioxane at the end of the reaction was 0.17 wt % (trioxepane - not detected).
• EXAMPLE 3 The reaction was carried out as in Example 2 except 3.76 g (4.17 wt %) of nitrobenzene with 7.6 ppm water was added in place of nitromethane.
• Dioxolane with 14.9 ppm water was added at 0.20 g/min and formaldehyde at 1.13 g/min (8.07 g/min/1) over a 9 min. period; exotherm was to 55.5°C.
• Equilibrium dioxolane concentration was 1.16 wt % and biproduct trioxane and trioxepane at the end of the reaction were 2.25 and 0.40 wt %.
• EXAMPLE 4 The reaction was carried out as in Example 2 except 3.63 g (4.05 wt %) of 2-nitropropane with 1.4 ppm water was added in place of nitromethane. Dioxolane with 14.9 ppm water was added at 0.184 g/min and formaldehyde at

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• 1998
  • 1998-07-13 US US09/114,450 patent/US5942595A/en not_active Expired - Fee Related
  • 1998-08-18 DE DE69819905T patent/DE69819905T2/de not_active Expired - Fee Related
  • 1998-08-18 EP EP98942085A patent/EP1003799B1/de not_active Expired - Lifetime
  • 1998-08-18 JP JP2000509757A patent/JP2001515108A/ja active Pending
  • 1998-08-18 WO PCT/US1998/017050 patent/WO1999009082A1/en active IP Right Grant
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